Tom Fahey

Evidence based purchasing: understanding results of clinical trials and systematic reviews

Abstract Objective: To assess whether the way in which the results of a randomised controlled trial and a systematic review are presented influences health policy decisions. Design: A postal questionnaire to all members of a health authority within one regional health authority. Setting: Anglia and Oxford regional health authorities. Subjects: 182 executive and non-executive members of 13 health authorities, family health services authorities, or health commissions. Main outcome measures: The average score from all health authority members in terms of their willingness to fund a mammography programme or cardiac rehabilitation programme according to four different ways of presenting the same results of research evidence—namely, as a relative risk reduction, absolute risk reduction, proportion of event free patients, or as the number of patients needed to be treated to prevent an adverse event. Results: The willingness to fund either programme was significantly influenced by the way in which data were presented. Results of both programmes when expressed as relative risk reductions produced significantly higher scores when compared with other methods (P<0.05). The difference was more extreme for mammography, for which the outcome condition is rarer. Conclusions: The method of reporting trial results has a considerable influence on the health policy decisions made by health authority members.

What constitutes controlled hypertension? Patient based comparison of hypertension guidelines

Abstract Objectives: To investigate and quantify the extent to which variations in guidelines influence assessment of control of hypertension. Design: Cross sectional study. Selected patients had hypertension assessed as controlled or uncontrolled with guidelines from New Zealand, Canada, the United States, Britain, and the World Health Organisation. Setting: 18 general practices in Oxfordshire. Subjects: 876 patients with diagnosed hypertension and taking antihypertensive drugs. Main outcome measures: Proportion of patients with controlled hypertension according to each set of guidelines. Results: The proportion of patients with controlled hypertension varied from 17.5% to 84.6% with the different guidelines after adjustment for the sampling method. All five sets of guidelines agreed on the classification for 31% (277) of the patients. The New Zealand guidelines calculate an absolute risk of a cardiovascular event. When this was taken as the standard half of the patients with uncontrolled hypertension by the United States criteria would be treated unnecessarily and 31% of those classified as having controlled hypertension by the Canadian guidelines would be denied beneficial treatment. Conclusions: Hypertension guidelines are inconsistent in their recommendations and need to make clear the absolute benefits and risks of treatment. Key messages This study applied the recommendations of guidelines from New Zealand, Canada, the United States, Britain, and the WHO to a sample of 879 hypertensive patients The proportion with controlled hypertension varied between 17.5% and 84.6% according to which set of guidelines was followed Overall, the five sets of guidelines agreed for 31% of the patients Hypertension guidelines are inconsistent and unclear on the absolute benefits of treatment

Inter-rater agreement in the scoring of abstracts submitted to a primary care research conference

BackgroundChecklists for peer review aim to guide referees when assessing the quality of papers, but little evidence exists on the extent to which referees agree when evaluating the same paper. The aim of this study was to investigate agreement on dimensions of a checklist between two referees when evaluating abstracts submitted for a primary care conference.MethodsAnonymised abstracts were scored using a structured assessment comprising seven categories. Between one (poor) and four (excellent) marks were awarded for each category, giving a maximum possible score of 28 marks. Every abstract was assessed independently by two referees and agreement measured using intraclass correlation coefficients. Mean total scores of abstracts accepted and rejected for the meeting were compared using an unpaired t test.ResultsOf 52 abstracts, agreement between reviewers was greater for three components relating to study design (adjusted intraclass correlation coefficients 0.40 to 0.45) compared to four components relating to more subjective elements such as the importance of the study and likelihood of provoking discussion (0.01 to 0.25). Mean score for accepted abstracts was significantly greater than those that were rejected (17.4 versus 14.6, 95% CI for difference 1.3 to 4.1, p = 0.0003).ConclusionsThe findings suggest that inclusion of subjective components in a review checklist may result in greater disagreement between reviewers. However in terms of overall quality scores, abstracts accepted for the meeting were rated significantly higher than those that were rejected.

Relationship between medication adherence and blood pressure in primary care: prospective study

There is good evidence from randomised trials (RCTs) that treating high blood pressure is effective in reducing cardiovascular risk, but people with high blood pressure can find it difficult to take antihypertensive medication regularly. The relationship between adherence and achieved blood pressure is far from clear.

Randomized trial evaluating the framing of cardiovascular risk and its impact on blood pressure control [ISRCTN87597585]

BackgroundThe format or frame in which the results of randomized trials are presented has been shown to influence health professionals self-reported practice. We sought to investigate the effect of framing cardiovascular risk as two different formats in a randomized trial.MethodsWe recruited 457 patients aged between 60 and 79 years with high blood pressure from 20 family practices in Avon, UK. Patients were randomized to cardiovascular risk presented either as 1) an absolute risk level (AR) or as 2) the number needed to treat to prevent an adverse event (NNT). The main outcome measures were: 1) percentage of patients in each group with a five-year cardiovascular risk ≥ 10%, 2) systolic and diastolic blood pressure, 3) intensity of prescribing of cardiovascular medication.ResultsPresenting cardiovascular risk as either an AR or NNT had no impact reducing cardiovascular risk at 12 month follow up, adjusted odds ratio 1.53 (95%CI 0.76 to 3.08). There was no difference between the two groups in systolic (adjusted difference 0.97 mmHg, 95%CI -2.34 mmHg to 4.29 mmHg) or diastolic (adjusted difference 0.70 mmHg, 95%CI -1.05 mmHg to 2.45 mmHg) blood pressure. Intensity of prescribing of blood pressure lowering drugs was not significantly different between the two groups at six months follow up.ConclusionsPresenting cardiovascular risk in clinical practice guidelines as either an AR or NNT had a similar influence on patient outcome and prescribing intensity. There is no difference in patient outcomes when these alternative formats of risk are used in clinical practice guidelines.

Reconciling different measures of risk in the treatment of hypertension: a community-based study

Background: There is disagreement as to how cardiovascular risk in hypertensive patients should be measured. In particular, whether absolute risk measurement alone is a realistic index on which to base treatment goals. Method: A cross-sectional study on 895 treated hypertensive patients in 18 general practices in the UK. Reporting on the distribution and magnitude of age- specific absolute risk. The percentage of individuals with controlled hypertension whose absolute risk exceeds their age/sex absolute risk standard and the percentage of individuals with uncontrolled hypertension whose risk is less than their age/sex absolute risk standard. Results: Overall, 62.8% (95% CI 59.6–66%) individuals had an absolute risk that exceeded 20% over 10 years. The magnitude of absolute risk was considerable (range 3.5–87.8%) and increasing absolute risk was significantly associated with age. Of those individuals with controlled hypertension 50.5% (95% CI 45.1–55.8%) had an absolute risk which exceeded their age/sex absolute risk standard. Conversely, 30.4% (95% CI 26.6–34.2%) of those with uncontrolled hypertension had an absolute risk that was less than their age/sex absolute risk standard. Conclusions: The distribution and magnitude of absolute risk is significantly associated with age. Appreciation of such a relationship is needed when setting realistic treatment goals according to an absolute risk standard, particularly in the elderly. In addition, the use an age/sex absolute risk standard is likely to further modify treatment goals in individuals at high and low absolute risk of cardiovascular disease.